The operator who operates the conventional NC apparatus performs a trial operation of a processing program using a single block and an override at the time of processing immediately after completing the set-up of the workpiece and the tool. At this time, the operator visually checks whether or not the correct tool is mounted in exchanging the tool. Then, when the tool approaches the workpiece, the operator once stops the tool prior to getting to the workpiece to confirm the residual movement amount displayed on the display screen of the NC apparatus. Moreover, the operator judges whether or not there is any problem with a tool number command (T command) of the processing program, a tool compensation number command (D number) of the processing program, and a tool offset number command (H number), a set value of the tool compensation amount, and a set value of the tool offset. If there is no problem, the operator checks the processing program to continue the processing.
However, in the case where a plurality of tools are commanded in one processing program, it was required to make the above confirmation for all the tools in the order. At this time, the operator accustomed to the operation may neglect the confirmation for all the tools, and perform the processing by mistaking the tool offset or the tool number. Furthermore, the tool is struck against the workpiece at the fast feed, damaging the bearings of the principal axis, or causing a burn-in of the principal axis to lead to a failure or breakage of the machine tool in some cases.
Thus, a method for overcoming this problem may be employed, in which the processing program is divided into every process of tool exchange, with the sequence number being attached to every divided process, whereby the above confirmation is made by searching the sequence number for each process.
Also, another method may be employed in which an optional stop instruction for temporarily suspending the execution of program is inserted into every process, and the above confirmation is made for each tool while interrupting the execution of program.
However, the method for searching the sequence number for each process had a problem that it took much labor to attach the sequence number to the portion to be searched, and further search the sequence number. Also, with this method, if the processing program for allowing the next tool to be ready at the standby position of a magazine in advance by commanding the next tool number during the execution of the current process in order to shorten the processing time, there was a problem that the processing program can not be checked, because the tool number is commanded before the location search by the sequence number.
Also, in the method for inserting the optional stop instruction into every process, the operator needed to confirm the end of each process one by one, and insert the optional stop instruction to give rise to a dead time.